Household beverage producing machines, in particular coffee producing machines, are becoming more and more popular. Some beverage producing machines are relatively simple and provide only for the production of coffee, such as fresh-brew coffee or espresso coffee. Other more developed beverage producing devices and systems are designed for producing coffee-based beverages comprising milk, such as cappuccino, latte macchiato and similar coffee and milk containing beverages.
A system for producing such kind of beverages is disclosed for example in WO-A-2010/044116. This known beverage producing system comprises a beverage producing machine and a jug for containing milk. The jug is provided with a milk emulsifier or milk frothing device. The beverage producing machine is provided with a steam nozzle which is arranged in a recess and is downwardly oriented so that it can be introduced into a corresponding steam inlet provided on top of the jug. To enable the insertion movement, the steam nozzle is slanted and oriented so as to project outside the recess provided on the coffee producing machine. The hot and pressurized steam delivered by the coffee producing machine through the steam nozzle is processed in a Venturi tube of the emulsifier to suck milk from the jug and heat the milk. The emulsifier is further provided with an air port, through which air can be sucked and mixed with the milk to form an air-milk froth which is heated by the steam. The air port can be selectively closed or opened, depending on whether the hot milk or hot and emulsified milk is required. The hot and optionally emulsified milk is then dispensed from the jug into a cup.
In order to prevent any hazard due to accidental dispensing of hot steam, these known beverage producing systems are provided with sensors capable of detecting whether a milk jug is properly connected to the coffee machine. Only if the jug is correctly positioned and connected to the steam nozzle of the coffee producing machine, steam delivery is enabled. This prevents the risk of hot stem being ejected from the steam nozzle against the user.
These sensors, which are required for safety purposes, increase substantially the cost of the machine, also because they have to be interfaced with a control unit and the latter must be suitably programmed to control the enablement of the steam dispensing cycle based upon the signal received from the sensors.